Compilare: user.cpp: In function ‘int main()’: user.cpp:44:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k=0;k<primes.size();++k) { ^ user.cpp:17:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("nummst.in","r",stdin); ^ user.cpp:18:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("nummst.out","w",stdout); ^ user.cpp:19:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&N); ^